The present invention relates generally to transducer devices of the dynamic type, such as speakers and microphones, which utilize a relatively movable permanent magnet and an associated electric coil winding.
Heretofore, well known types of transducers in the form of microphones have in general comprised one of the following types:
A. A ceramic microphone in which a ceramic wafer produces an output current in response to received vibrations. This is considered to be a superior type and is relatively the most expensive, and requires a pre-amplifier in its use. PA1 B. Moving coil type in which a coil is carried by a diaphragm and moved in response to picked up vibrations with respect to a fixed magnet. This type is considered as the next best type and is less expensive than the ceramic type. PA1 C. The fixed coil type in which the coil surrounds a core magnet having a tin disc diaphragm supported at one end thereof, vibrations of the diaphragm serving to vary the reluctance of the magnetic circuit threading the coil turns. This is considered the poorest and least expensive of the microphone types.
The present invention comprises an improvement over the above enumerated types in that it incorporates a relatively simple but highly efficient transducer structure of the dynamic type, which embodies a vibratable diaphragm that can be attached in contact with a surface of a vibratable body, and more particularly with a resonator surface of a musical instrument such as, for example, a guitar, base viol, cello, banjo and the like, the diaphragm supporting a permanent magnet which is surrounded by an electric coil winding, the magnet and coil being relatively movable. It is a primary feature of the present invention that the coil is isolated with respect to vibrations of the diaphragm, so that the generated signals will be substantially free of distortions.